My wife and adopted a 7 year old guy from BRAT this past December and he does the same thing. He's a retired puppy mill stud that never learned how to climb stairs until he was "freed." If he gets a running start, he can leap a step or two, but if he walks up to steps, he goes up backwards, just like in the video. He also has a phobia with certain door thresholds. But don't worry. He's a super fun little guy who just has a few little quirks. He can outrun his 12 year old B-sister in the yard, but she always beats him up the stairs.
